Polymer interlayers having improved sound insulation properties

ABSTRACT

A polymer interlayer comprising a layer comprising a poly(vinyl acetal) resin having a residual hydroxyl content and a residual acetate content, and a plasticizer, wherein the residual hydroxyl content, the residual acetate content and the plasticizer are selected such that the polymer interlayer has at least one glass transition temperature less than about 20° C. and a peak tan delta of greater than 1.33, and a glass panel having a configuration of 2.3-mm glass//interlayer//2.3-mm glass and at 20° C. has a transmission loss, TL w , of greater than 42 decibels as measured by weighted average sound transmission loss at 2000 to 8000 Hz, and a transmission loss, TL c , of greater than 38 decibels at the coincident frequency is disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure is related to the field of polymer interlayers formultiple layer panels and multiple layer panels having at least onepolymer interlayer sheet. Specifically, this disclosure is related tothe field of polymer interlayers having improved sound insulationproperties, and more specifically, to polymer interlayers havingimproved sound insulation properties for use in vehicle and buildingglazings.

2. Description of Related Art

Occupants of buildings, especially in areas near airports, railways, andhuman activities, or where street and highway traffic noise is aproblem, are increasingly interested in acoustic insulating glazing.

Automobile designers are also aware that a barrier to designing quietercar interiors is the acoustic limitations of automotive glass. Asautomobile manufacturers have increased their efforts to design andbuild quieter cars and reduce vehicle interior noise through thetreatment of passenger compartment boundaries with sound-attenuatingpackages, automotive glazing has become the primary transmission path ofwind noise, external airborne noise and structure-borne noise, and it isa major contributor to the consumer's perception of vehicle interiornoise level.

Laminated glass, made of a poly(vinyl butyral) (PVB) plastic interlayersandwiched by two panes of glass sheet, has long served for safetypurposes and is commonly utilized in architectural window applicationsand in the windows of motor vehicles and airplanes. The main function ofthe interlayer in the laminated safety glass is to absorb energyresulting from impact or force applied to the glass, to keep the layersof glass bonded even when the force is applied and the glass is broken,and to prevent the glass from breaking up into sharp pieces. Less knownis the advantage of laminated glass for noise attenuation. Over the pastdecades, architectural use of PVB laminated glass in buildings nearairports and railways has served to reduce the noise levels inside thebuildings, making it more comfortable for the occupants. Likewise thistechnology is now being used in buildings where street and highwaytraffic noise is a problem. Recently, advances in interlayer technologyhave made improved laminated glass that provides noise, vibration, andharshness improvements for automotive glass.

The sound insulation property of a glass panel can be characterized bySound Transmission Loss (STL). It is well known that sound transmissionthrough glass exhibits coincident effect. Glass has a specific criticalor coincident frequency at which the speed of an incident acousticalwave in air matches that of a glass bending wave. At the coincidentfrequency, the acoustic wave is especially effective at causing glass tovibrate, and the vibrating glass is an effective sound radiator at ornear the coincident frequency and at frequencies above or below thecoincident frequency. As a result, glass exhibits a dip or decrease insound transmission loss, referred to as the coincidence dip orcoincident effect, and the glass becomes transparent to sound.

The coincident frequency can be represented by the following equation(1):

f _(c) =c ²/2π×[ρ_(s) /B] ^(1/2)  (1)

where c is the sound speed in air, ρ_(s) is the surface density of theglass panel, and B is the bending stiffness of glass panel. In general,the coincident frequency increases with decreasing thickness of theglass panel. For automotive glazings, the coincident frequency istypically in the range of 3150 to 6000 Hz, which is well within the windnoise frequency region of 2000 to 8000 Hz. For laminated architecturalbuilding glass (such as windows), the coincident frequency is generallyless than about 3150 Hz.

The coincident effect not only results in a dip or decrease in soundtransmission loss at the coincident frequency, but also reduces soundtransmission loss at frequencies above and below the coincidentfrequency. Glass panels exhibiting severe coincident effect (low STL) atthe coincident frequency will transmit sound more dominantly at thatfrequency, resulting in an enclosed area (such as the interior of a caror a room in a building) with high sound intensity at or near thecoincident frequency. It is therefore important to characterize thesound insulation properties of a glass panel by weight averaging itssound transmission loss in the frequency of interest, such as in thecoincident frequency region, and the sound transmission loss at thecoincident frequency (as further described herein).

The thermoplastic polymer found in safety glass can consist of a singlelayer of a thermoplastic polymer, such as poly(vinyl acetal) orpoly(vinyl butyral) (PVB), that has had one or more physicalcharacteristics modified in order to increase acoustic dampening andreduce the sound transmission through the glass. Conventional attemptsat such acoustic dampening have included using PVB interlayers with lowglass transition temperatures. Other attempts have included multilayerinterlayers having two adjacent layers of thermoplastic polymer whereinthe layers have dissimilar characteristics (see, for example U.S. Pat.Nos. 5,340,654, 5,190,826, and 7,510,771). These multilayer interlayerstypically comprise a soft inner or core layer and two stiffer outer orskin layers. The soft core layer provides acoustic damping properties,while the stiff skin layers provide handling, processability, andmechanical strength of the interlayer.

Despite these advances, there is a continued need to further improve theacoustic properties and reduce the sound or noise transmission throughthe coincident frequency region, especially in the wind noise frequencyregion. Accordingly, there is a need in the art for the development ofan interlayer, either a monolithic or a multilayer interlayer, thatprovides improved acoustic or sound insulation properties without areduction in other optical, mechanical, and physical characteristics ofan interlayer, and a need for the development of polymer interlayersincluding monolithic and multilayer interlayers that provide improvedacoustic properties for glass panels when used in vehicle and buildingglazings.

SUMMARY OF THE INVENTION

Because of these and other problems in the art, described herein, amongother things is a polymer interlayer comprising: at least a soft layerwhere the interlayer has improved sound insulation properties. Thepolymer interlayer comprises a poly(vinyl acetal) resin having aresidual hydroxyl content and a residual acetate content, and aplasticizer, wherein the polymer interlayer has excellent acousticproperties and sound insulation properties. The polymer interlayer maybe a single (monolithic) layer or a multilayer polymer interlayer.

In an embodiment, a polymer interlayer comprises: a layer comprising apoly(vinyl acetal) resin having a residual hydroxyl content and aresidual acetate content, and a plasticizer, wherein the residualhydroxyl content, the residual acetate content and the plasticizer areselected such that the polymer interlayer has a glass transitiontemperature less than about 20° C. and a peak tan delta of greater than1.33, and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

In embodiments, the plasticizer comprises an aromatic moiety.

In embodiments, the polymer interlayer further comprises a secondpoly(vinyl acetal) resin. In embodiments, the polymer interlayer furthercomprises a second layer. In embodiments, the second layer comprises asecond poly(vinyl acetal resin) and a second plasticizer.

In an embodiment, a polymer interlayer comprises: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has a glass transitiontemperature less than about 20° C. and a peak tan delta of greater than1.33, and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

In an embodiment, at least one of the difference between the firstresidual hydroxyl content and the second residual hydroxyl content andthe difference between the first residual acetate content and the secondresidual acetate content is at least 2.0 weight percent.

In an embodiment, a polymer interlayer comprises: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has a glass transitiontemperature less than about 20° C. and a peak tan delta of greater than1.33; and wherein at least one of the difference between the firstresidual hydroxyl content and the second residual hydroxyl content andthe difference between the first residual acetate content and the secondresidual acetate content is at least 2.0 weight percent, and a glasspanel having a configuration of 2.3-mm glass//interlayer//2.3-mm glassand at 20° C. has a transmission loss, TL_(w), of greater than 42decibels as measured by weighted average sound transmission loss at 2000to 8000 Hz, and a transmission loss, TL_(c), of greater than 38 decibelsat the coincident frequency.

In an embodiment, a polymer interlayer comprises: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has a glass transitiontemperature less than about 20° C. and a peak tan delta of greater than1.33; and wherein the difference between the first residual hydroxylcontent and the second residual hydroxyl content is at least 2.0 weightpercent, and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

In an embodiment, a polymer interlayer comprises: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has a glass transitiontemperature less than about 20° C. and a peak tan delta of greater than1.33; and wherein the difference between the first residual acetatecontent and the second residual acetate content is at least 2.0 weightpercent, and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

In embodiments, the polymer interlayer has a sound insulation, TL_(w),greater than 42.5 decibels, or greater than 43 decibels, or greater than44 decibels, or greater than 45 decibels, or greater than 46 decibels asmeasured by weighted average sound transmission loss at 2000 to 8000 Hz.In embodiments, the polymer interlayer has sound insulation, TL_(c), ofgreater than 38 decibels at the coincident frequency, or greater than 39decibels, or greater than 40 decibels, or greater than 41 decibels atthe coincident frequency.

In an embodiment, a polymer interlayer comprises: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has a glass transitiontemperature less than about 20° C. and a peak tan delta of greater than1.33; and wherein the difference between the first residual hydroxylcontent and the second residual hydroxyl content is at least 2.0 weightpercent and the difference between the first residual acetate contentand the second residual acetate content is at least 2.0 weight percent,and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

In embodiments, the first plasticizer and the second plasticizer are thesame. In embodiments, the first plasticizer and the second plasticizerare different. In embodiments, at least one of the first plasticizer andthe second plasticizer comprises an aromatic moiety.

In embodiments, the polymer interlayer has a glass transitiontemperature less than about 19° C., or less than 18° C., or less than17° C., or less than 16° C., or less than 15° C., or less than 12° C.,or less than 10° C. In embodiments, the polymer interlayer has a peaktan delta of greater than 1.34, or greater than 1.35, or greater than1.36, or greater than 1.37, or greater than 1.38, or greater than 1.39,or greater than 1.40, or greater than 1.42, or greater than 1.45, orgreater than 1.50, or greater than 1.60.

In embodiments, the difference between the first residual hydroxylcontent and the second residual hydroxyl content is at least 3.0 weightpercent and the difference between the first residual acetate contentand the second residual acetate content is at least 3.0 weight percent.In embodiments, the difference between the first residual hydroxylcontent and the second residual hydroxyl content is at least 4.0 weightpercent, or at least 5.0 weight percent, or at least 6.0 weight percent,or at least 7.0 weight percent, or at least 8.0 weight percent, or atleast 9.0 weight percent, or at least 10.0 weight percent, or at least12.0 weight percent, or at least 15.0 weight percent, or at least 18.0weight percent, or at least 21.0 weight percent, or at least 24.0 weightpercent, or at least 28.0 weight percent. In embodiments, the differencebetween the first residual acetate content and the second residualacetate content is at least 4.0 weight percent, or at least 5.0 weightpercent, or at least 6.0 weight percent, or at least 7.0 weight percent,or at least 8.0 weight percent, or at least 9.0 weight percent, or atleast 10.0 weight percent, or at least 12.0 weight percent, or at least14.0 weight percent, or at least 16.0 weight percent, or at least 18.0weight percent, or at least about 20.0 weight percent, or at least 24.0weight percent, or at least 29.0 weight percent.

A multiple layer panel is also disclosed. The multiple layer panelcomprises at least one rigid substrate, and a polymer interlayer ormultiple layer polymer interlayer as disclosed herein. The panel hasimproved acoustic properties, and specifically improved sound insulationproperties.

A method of making a polymer interlayer is also disclosed, wherein theinterlayer is as disclosed herein. The polymer interlayer may be asingle layer or a multiple layer polymer interlayer.

In certain embodiments, the rigid substrate is glass. In otherembodiments, the panel may further comprise a photovoltaic cell, withthe interlayer encapsulating the photovoltaic cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart showing the sound transmission loss (STL) dataobtained at 20° C. for Glass Panels A to D in Table 1.

FIG. 2 is a chart showing the sound transmission loss (STL) dataobtained at 20° C. for Glass Panels E to G in Table 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Described herein, among other things, are interlayers comprised of athermoplastic resin, and at least one plasticizer, wherein theinterlayers have been produced to have improved acoustic properties,such as improved sound insulation. Also described are multiple layerglass panels comprising the interlayers, and methods of making thepolymer interlayers. The use of the thermoplastic polymer interlayer,when selected to have a glass transition temperature less than about 20°C. and a peak tan delta (tan δ) of greater than 1.33, results in aninterlayer having excellent sound insulation properties, as measured byat least Sound Transmission Loss (STL). As a result, sound reducingmultiple layer glass panels are produced.

Acoustic performance in a glass panel, such as a windshield or abuilding window, has been achieved by providing a soft interlayer, or ina multilayer, a softer core layer and stiffer outer or skin layers. Ithas been determined by the inventors that improved acoustic performance,such as increased Sound Transmission Loss and better sound insulation,can be achieved by changing other properties of the interlayer, whichthen changes the properties of a glass panel containing the interlayer.The inventors have discovered that when the glass transition temperatureof an interlayer is less than about 20° C., there is a correlationbetween sound insulation of a glass panel and the peak tan delta (tan δ)of an interlayer (or the core layer of a multilayer interlayer). Thepeak tan delta can be controlled and increased by selecting specificmaterials and formulating the interlayer as further described below.

As used herein, the terms “multilayer” and “multiple layers” mean aninterlayer having more than one layer, and multilayer and multiple layermay be used interchangeably. The layers of the interlayer are generallyproduced by mixing a polymer resin such as poly(vinyl butyral) with oneor more plasticizers and melt processing the mix into a sheet by anyapplicable process or method known to one of skill in the art,including, but not limited to, extrusion, with the layers being combinedby processes such as co-extrusion and lamination. Other additionalingredients may optionally be added for various other purposes. Afterthe interlayer sheet is formed, it is typically collected and rolled fortransportation and storage and for later use in the multiple layer glasspanel, as discussed below.

Multilayer interlayers, such as an interlayer having two or more layers(such as a trilayer interlayer having three layers) can comprise atleast one soft layer and at least one stiff layer. The soft layer(s) isoften the inner or core layer in interlayers having at least threelayers. Some terminology used throughout this application will beexplained to provide a better understanding of the invention. The terms“polymer interlayer sheet,” “interlayer,” “polymer layer”, and “polymermelt sheet” as used herein, generally may designate a single-layer sheetor a multilayered interlayer. A “single-layer sheet,” as the nameimplies, is a single polymer layer extruded as one layer. A multilayeredinterlayer, on the other hand, may comprise multiple layers, includingseparately extruded layers, co-extruded layers, or any combination ofseparately and co-extruded layers. Thus the multilayered interlayercould comprise, for example: two or more single-layer sheets combinedtogether (“plural-layer sheet”); two or more layers co-extruded together(“co-extruded sheet”); two or more co-extruded sheets combined together;a combination of at least one single-layer sheet and at least oneco-extruded sheet; a combination of a single-layer sheet and aplural-layer sheet; and a combination of at least one plural-layer sheetand at least one co-extruded sheet. In various embodiments of thepresent disclosure, a multilayered interlayer comprises at least twopolymer layers (e.g., a single layer or multiple layers co-extrudedand/or laminated together) disposed in direct contact with each other,wherein each layer comprises a polymer resin, as detailed more fullybelow. As used herein for multilayer interlayers having at least threelayers, “skin layer” generally refers to the outer layers of theinterlayer and “core layer” generally refers to the inner layer(s).Thus, one exemplary embodiment would be: skin layer//core layer//skinlayer. In the multilayer interlayers having skin layer//core layer//skinlayer configuration, in some embodiments the skin layer maybe stifferand the core layer may be softer, while in other embodiments the skinlayer may be softer and the core layer may be stiffer. It should benoted, however, further embodiments include interlayers having only twolayers or interlayers having more than three layers (e.g., 4, 5, 6, orup to 10 or more individual layers). Additionally, any multilayerinterlayer utilized can be varied by manipulating the composition,thickness, or positioning of the layers and the like. For example, inone trilayer polymer interlayer sheet, the two stiff (or outer or skin)layers may comprise poly(vinyl butyral) (“PVB”) resin with a plasticizeror mixture of plasticizers, while the softer (inner or core) layers maycomprise the same or different PVB resin or a different thermoplasticmaterial with a the same or different plasticizer and/or mixture ofplasticizers. Thus, it is contemplated that the stiff or skin layers andthe soft or core layer(s) of the multilayered interlayer sheets may becomprised of the same thermoplastic material or different thermoplasticmaterials and the same or different plasticizer or plasticizers. Eitheror both layers may include additional additives as known in the art, asdesired.

As used herein, the sound insulation property of a glass panel in thefrequency region of interest can be represented by the weighted averagetransmission loss (TL), or TL_(w). The TL_(w) of a glass panel at 2000to 8000 Hz is obtained from the equation (2):

TL _(w)=10×log((Σ(10^(TL) i ¹⁰))/k)  (2)

where TL_(i) is the transmission loss (TL) at ⅓ octave frequency band iin the frequency region from 2000 to 8000 Hz; i=1 to k, k is the numberof ⅓ octave bands from 2000 to 8000 Hz (k=7). Glass panels having bettersound insulation will have a higher TL_(w) and Sound Transmission Lossat the coincident frequency (TL_(c)); conversely, glass panels havingeither lower TL_(w) or TL_(c) or both lower TL_(w) and TL_(c) will havepoorer sound insulation.

As used herein, “Sound Transmission Loss” in the frequency region from2000 to 8000 Hz is determined for a laminate containing an interlayer,such as the interlayer of the present invention or a comparativeinterlayer, in accordance with ASTM E90 (2009) at a fixed temperature of20° C. The interlayers are laminated with 2.3 mm clear glass (having aconfiguration of 2.3 mm glass//interlayer//2.3 mm glass). The glasspanel has dimensions of 50 cm by 80 cm. The sound transmission lossmeasurements of the test panel at 2000, 2500, 3150, 4000, 5000, 6300,and 8000 Hz are used to calculate the weighted average soundtransmission loss (TL_(w)) according to equation (2) in the frequencyregion of 2000 to 8000 Hz.

The present invention also discloses a multilayer interlayer comprising(a) a stiffer layer, (b) a softer layer comprising a polyvinyl butyralresin having a residual hydroxyl content less than about 15 weightpercent (wt. %), and (c) a plasticizer, wherein the interlayer has atleast one glass transition temperature less than about 20° C. and peaktan delta (tan δ) of greater than 1.33, and the glass panels comprisingthe interlayer of the present invention and having a 2.3-mmglass//interlayer//2.3-mm glass configuration have a sound insulation,TL_(w), at 20° C., of greater than 42 decibels as measured by weightedaverage sound transmission loss at 2000 to 8000 Hz, and a TL_(c) greaterthan 38 decibels at the coincident frequency.

As used herein, the tan delta (tan δ) can be obtained from the glasstransition of a polymer interlayer. Glass transition of a polymerinterlayer is the state from the “glassy” state into the rubbery state,which is reversible; the glass transition temperature is the temperaturethat marks the transition from the glassy state to the rubbery state. Atthe glass transition state, the polymer interlayer provides the highestacoustic damping, and the glass transition temperature is used tocharacterize the acoustic insulation property of the polymer. The glasstransition temperature (T_(g)) can be determined by dynamical mechanicalthermal analysis (DMTA) in shear mode. The DMTA measures the storage(elastic) modulus (G′) in Pascals, loss (viscous) modulus (G″) inPascals, tan delta (=G″/G′) of the specimen as a function of temperatureat a given frequency, and temperature sweep rate. A frequency of 1 Hzand temperature sweep rate of 3° C./min were used herein. The T_(g) isthen determined by the position of the tan delta peak on the temperaturescale in ° C. and the tan delta peak value is referred as tan delta orpeak tan delta. As used herein, “tan delta”, “peak tan delta”, “tan δ”and “peak tan δ” may be used interchangeably.

As used herein, a “soft layer” or “softer layer” is the layer having aglass transition temperature less than about 20° C. As used herein, a“stiff layer” or “stiffer layer” generally refers to a layer that isstiffer or more rigid than another layer and that has a glass transitiontemperature that is generally at least two degrees C. (2° C.) higherthan another layer (such as the softer layer).

In embodiments, the interlayer comprises a soft polymer layer comprisinga plasticizer having one or more aromatic moieties. It has beendiscovered that the use of a plasticizer having one or more aromaticmoieties significantly increases the tan delta of the interlayercompared to interlayers having only a conventional plasticizer withoutaromatic moieties, as further discussed below. In embodiments, theplasticizer may be a high refractive index plasticizer.

In various embodiments, the polymer interlayer comprises a soft layerthat exhibits at least one glass transition less than about 20° C., orless than about 19° C., or less than about 18° C., or less than about17° C., or less than about 16° C., or less than about 15° C., or lessthan about 10° C., or less than about 5° C., or less than about 0° C.,or less than about −5° C., or less than about −10° C. In embodiments,the tan delta is greater than 1.33, or greater than 1.34, or greaterthan 1.35, or greater than 1.36, or greater than 1.37, or greater than1.38, or greater than 1.39, or greater than 1.40, or greater than 1.45,or greater than 1.50, or greater than 1.55, or greater than 1.60, orgreater than 1.65, or greater than 1.70, or greater than 1.75, orgreater than 1.80, or greater than 1.85, or greater than 1.90, orgreater than 1.95, or greater than 2.00.

In various embodiments, the interlayers of the present invention, whenused in a glass panel having a 2.3-mm glass//interlayer//2.3-mm glassconfiguration at 20° C. have sound insulation, TL_(w), greater than 42.5decibels (“dB”), or greater than 43 decibels, or greater than 44decibels, or greater than 45 decibels, or greater than 46 decibels asmeasured by weighted average sound transmission loss at 2000 to 8000 Hz.In various embodiments, the interlayers of the present invention havesound insulation, TL_(c), (when in a glass panel having a 2.3-mmglass//interlayer//2.3-mm glass configuration and at 20° C.) of greaterthan 38 decibels at the coincident frequency, or greater than 39decibels, or greater than 40 decibels, or greater than 41 decibels atthe coincident frequency.

In various embodiments, the polymer interlayer comprises a poly(vinylacetal) resin layer. In other embodiments, when the polymer interlayercomprises at least a first polymer layer and a second polymer layer, atleast one of the polymer layers comprises a poly(vinyl acetal) resin,such as poly(vinyl butyral), and a plasticizer. In further embodiments,all polymer layers comprise poly(vinyl acetal) resins or poly(vinylbutyral) resins and plasticizers. The residual hydroxyl and residualacetate contents in at least one of the poly(vinyl acetal) resins andthe type and amount of plasticizer(s) to be mixed with the resin(s) areselected such that the glass transition temperature of the resultinglayer is less than about 20° C. and tan delta (tan δ) is greater than1.33.

As used herein, residual hydroxyl content (calculated as % vinyl alcoholcontent or poly(vinyl alcohol) (PVOH) by weight) in poly(vinyl acetal)refers to the amount of hydroxyl groups remaining on the polymer chainsafter processing is complete. For example, poly(vinyl butyral) (PVB) canbe manufactured by hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol(PVOH), and then reacting the PVOH with butyraldehyde. In the process ofhydrolyzing the poly(vinyl acetate), typically not all of the acetateside groups are converted to hydroxyl groups. Further, reaction withbutyraldehyde typically will not result in all hydroxyl groups beingconverted to acetal groups. Consequently, in any finished PVB resin,there typically will be residual acetate groups (as vinyl acetategroups) and residual hydroxyl groups (as vinyl hydroxyl groups) as sidegroups on the polymer chain. As used herein, residual acetate content(calculated as % vinyl acetate content or poly(vinyl acetate) (PVAc) byweight in poly(vinyl acetal)) refers to the amount of residual acetategroups remaining on the polymer chains. As used herein, residualhydroxyl content and residual acetate content is measured on a weightpercent basis per ASTM D1396.

In various embodiments, the polymer interlayer comprises a soft layercomprising a plasticizer having one or more aromatic moiety. Examples ofthe plasticizer having one or more aromatic moiety include, but are notlimited to, dipropylene glycol dibenzoate, tripropylene glycoldibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate,2-ethylhexyl benzoate, diethylene glycol dibenzoate, propylene glycoldibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, diethylene glycol di-o-toluate, triethylene glycoldi-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate,tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bis-phenolA bis(2-ethylhexaonate), ethoxylated nonylphenol,bis-(methoxyethyl)terephthalate, bis-(butoxyethyl)terephthalate,bis-(butoxyethoxyethyl)terephthalate,bis-(ethoxyethoxyethyl)terephthalate,bis-(2ethylhexyloxyethyl)terephthalate, 2-ethylhexyloxyethyl benzoate,2-ethylhexyloxyethoxyethyl)benzoate, ethoxyethoxyethyl benzoate,butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, andmixtures thereof. In some embodiments, examples of plasticizers havingone or more aromatic moiety are dipropylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate,bis-(butoxyethyl)terephthalate, bis-(butoxyethoxyethyl)terephthalate,tripropylene glycol dibenzoate, and mixtures thereof.

In various embodiments, the polymer interlayer comprises a soft layercomprising at least one plasticizer having one or more aromatic moietyand at least one conventional plasticizer. In other embodiments, thesoft layer comprises at least one conventional plasticizer. As usedherein, a “conventional plasticizer” is a plasticizer having no aromaticmoiety. Examples of conventional plasticizers include, but not limitedto, triethylene glycol di-(2-ethylhexanoate) (“3GEH”), triethyleneglycol di-(2-ethylbutyrate), triethylene glycol diheptanoate,tetraethylene glycol diheptanoate, tetraethylene glycoldi-(2-ethylhexanoate), dihexyl adipate, dioctyl adipate, hexylcyclohexyladipate, diisononyl adipate, heptylnonyl adipate, dibutylsebacate, dioctyl sebacate, di(butoxyethyl) adipate, andbis(2-(2-butoxyethoxy)ethyl) adipate, and mixtures thereof.

In various embodiments of interlayers of the present disclosure, theinterlayer comprises a soft layer comprising about 0 to 100, about 10 toabout 80 phr, about 20 to about 70 phr, about 30 to about 60 phr, orgreater than 5 phr, or greater than 10 phr, or greater than 15 phr, orgreater than 20 phr, or greater than 25 phr, or greater than 30 phr, orgreater than 35 phr, or greater than 40 phr, or less than 100 phr, orless than 90 phr, or less than 80 phr, or less than 70 phr, or less than60 phr total plasticizer. As used herein, the amount of plasticizer, orany other component in the interlayer, can be measured as parts perhundred parts resin (phr), on a weight per weight basis. For example, if30 grams of plasticizer is added to 100 grams of polymer resin, then theplasticizer content of the resulting plasticized polymer would be 30phr. As used herein, when the plasticizer content of the interlayer isgiven, the plasticizer content is determined with reference to the phrof the plasticizer in the mix or melt that was used to produce theinterlayer.

While the ranges and limits of the residual hydroxyl and/or residualacetate contents of the poly(vinyl acetal) resins and the plasticizerused for the softer layer are selected such that the interlayer has aglass transition temperature less than about 20° C. and a tan delta ofgreater than 1.33 can be those previously discussed, in embodiments itis advantageous if the residual hydroxyl and residual acetate contentsof the poly(vinyl acetal) resins are selected such that the resins havehigh level of compatibility with a plasticizer. Poly(vinyl acetal)resins having higher or lower residual hydroxyl contents and/or residualacetate contents can, when combined with at least one plasticizer,ultimately include different amounts of plasticizer. The compatibilityof a given plasticizer with a poly(vinyl acetal) resin can depend, atleast in part, on the composition of the polymer, and, in particular, onits residual hydroxyl content. Overall, poly(vinyl acetal) resins withhigher residual hydroxyl contents tend to exhibit a lower compatibility(or capacity) for a given plasticizer as compared to similar resinshaving a lower residual hydroxyl content. As a result, poly(vinylacetal) resins with higher residual hydroxyl contents tend to be lessplasticized and exhibit higher stiffness than similar resins havinglower residual hydroxyl contents. Conversely, poly(vinyl acetal) resinshaving lower residual hydroxyl contents may tend to, when plasticizedwith a given plasticizer, incorporate higher amounts of plasticizer,which may result in a softer resin layer that exhibits a lower glasstransition temperature than a similar resin having a higher residualhydroxyl content. In this regard, it is desirable that the resins havinghigher compatibility with a plasticizer are chosen for the softer layeror interlayer of the present invention. In the multilayer interlayercomprising a softer layer and a stiffer layer, the resins having lowercompatibility with a plasticizer are chosen for the stiffer layer.Resins having higher compatibility with a plasticizer can generallyinclude resins having lower residual hydroxyl content and/or havingresidual acetate content greater than 4 wt. %, and these resins areparticularly useful for the softer layer, while resins having lowerresidual hydroxyl content and/or having residual acetate content greaterthan 4 wt. % require lower amounts of plasticizer to provide a softerlayer having glass transition temperature less than 20° C. and a higherpeak tan delta of greater than 1.33. For example, if two poly(vinylacetal) resins having the same residual acetate content and differentresidual hydroxyl contents (one of the resins has a lower residualhydroxyl content and the other resin has a higher residual hydroxyl) areeach individually plasticized with the same plasticizer to each form alayer or an interlayer having the same glass transition temperature of5° C., the layer with the lower residual hydroxyl content resin willrequire a lower amount of plasticizer than the layer with the higherresidual hydroxyl content to have the same glass transition temperatureof 5° C. The layer containing the lower level of plasticizer will have ahigher tan delta and the layer containing the higher level ofplasticizer will have a lower tan delta. As another example, if twopoly(vinyl acetal) resins having the same residual hydroxyl content anddifferent residual acetate contents (one resin has a lower residualacetate content and the other resin has a higher residual acetatecontent) are individually plasticized with the same plasticizer to eachfor a layer or an interlayer having the same glass transitiontemperature of 5° C., the layer with the lower residual acetate resinwill contain a higher amount of plasticizer than the layer having thehigher residual acetate content resin to form a layer having the sameglass transition temperature of 5° C. The layer containing the higheramount of plasticizer will have a lower tan delta than the layercontaining the lower amount of plasticizer will have a higher tan delta.The use of the resins having a lower residual hydroxyl content and/orhaving a residual acetate content greater than 4 wt. % in combinationwith a lower amount of plasticizer results in the softer layer having aglass transition temperature less than about 20° C. and a tan delta ofgreater than 1.33.

In embodiments, the residual hydroxyl content in the poly(vinyl acetal)resins and the amount of conventional plasticizer(s) are chosen suchthat the resulting softer layer has a glass transition temperature lessthan about 20° C. and a tan delta of greater than 1.33. The residualhydroxyl content can be at least about 7 wt. %, or at least about 8 wt.%, or at least about 9 wt. %, or at least about 10 wt. %, or at leastabout 11 wt. % and/or not more than about 15 wt. %, or not more thanabout 14 wt. %, or not more than about 13 wt. %, or not more than about11.5 wt. %, or not more than about 11 wt. %, or not more than about 10.5wt. %, or not more than about 10 wt. %, or not more than about 9.5 wt.%, or not more than about 9 wt. %, or in the range of from about 7 toabout 15 wt. %, or about 8 to about 14 wt. %, or about 9 to about 13 wt.%, and the plasticizer content can be less than about 80 phr, less thanabout 70 phr, less than about 60 phr, or less than about 50 phr, and/orgreater than about 10 phr, or greater than about 20 phr, or greater thanabout 30 phr. If the amount or level of plasticizer is 80 phr or more,the compatibility of the resin and plasticizer is reduced and tan deltaof the softer layer will be decreased to less than 1.33. In embodiments,a particularly useful range of plasticizer is from 45 to 70 phr, and aparticularly useful range for the residual hydroxyl content is from 8 to12 wt. %.

In embodiments, the residual hydroxyl content in the poly(vinyl acetal)resins and the amount of plasticizer(s) having at least one aromaticmoiety are chosen such that the resultant softer layer has a glasstransition temperature less than about 20° C. and tan delta of greaterthan 1.33. In this regard, the residual hydroxyl content can be at leastabout 7 wt. %, or at least about 8 wt. %, or at least about 9 wt. %, orat least about 10 wt. %, or at least about 11 wt. % and/or not more thanabout 15 wt. %, or not more than about 14 wt. %, or not more than about13 wt. %, or not more than about 11.5 wt. %, or not more than about 11wt. %, or not more than about 10.5 wt. %, or not more than about 10 wt.%, or not more than about 9.5 wt. %, or not more than about 9 wt. %, orin the range of from about 7 to about 15 wt. %, or about 8 to about 14wt. %, or about 9 to about 13 wt. %, and the plasticizer content can beless than about 100 phr, or less than about 90 phr, or less than about80 phr, or less than about 70 phr, or less than about 60, or less thanabout 50 phr and/or greater than about 10 phr, or greater than about 20phr, or greater than about 30 phr. In embodiments, a particularly usefulrange for the residual hydroxyl content is from 8 to 12 wt. %, and aparticularly useful range for the plasticizer content is from 70 to 100phr.

In embodiments, the residual acetate content in the poly(vinyl acetal)resins and the amount of plasticizer(s) can be chosen such that theresultant softer layer has a glass transition temperature less thanabout 20° C. and tan delta of greater than 1.33. In this regard, theresidual acetate content can be greater than 4 wt. %, or greater than 5wt. %, or greater than 6 wt. %, or greater than 7 wt. %, or greater than8 wt. %, or greater than 9 wt. %, or greater than 10 wt. %, or greaterthan 15 wt. %, greater than 20 wt. %, greater than 25 wt. %, or greaterthan 30 wt. %, and the plasticizer content can be less than about 80phr, or less than about 70 phr, or less than about 60 phr, or less thanabout 50 phr and/or greater than about 10 phr, or greater than about 20phr, or greater than about 30 phr. In embodiments, a particularly usefulrange for the residual acetate is from 10 to 18 wt. %. The plasticizercan be a conventional plasticizer or a plasticizer having one or morearomatic moiety or a mixture of two or more plasticizers. When theplasticizer is a conventional plasticizer, the particularly useful rangeof plasticizer is from 40 to 75 phr. When at least one plasticizerhaving at least one aromatic moiety is used, the amount of plasticizerin the interlayer is higher than the amount of plasticizer in theinterlayer not having a plasticizer with at least one aromatic moiety.

In embodiments, the residual acetate content and residual hydroxylcontent in the poly(vinyl acetal) resins and the amount ofplasticizer(s) can be chosen such that the resultant softer layer has aglass transition temperature less than about 20° C. and tan delta ofgreater than 1.33. In this regard, the residual acetate content can begreater than 4 wt. %, or greater than 5 wt. %, or greater than 6 wt. %,or greater than 7 wt. %, or greater than 8 wt. %, or greater than 9 wt.%, or greater than 10 wt. %, or greater than 15 wt. %, greater than 20wt. %, greater than 25 wt. %, or greater than 30 wt. %; the residualhydroxyl content can be at least about 7 wt. %, or at least about 8 wt.%, or at least about 9 wt. %, or at least about 10 wt. %, or at leastabout 11 wt. % and/or not more than about 15 wt. %, or not more thanabout 14 wt. %, or not more than about 13 wt. %, or not more than about11.5 wt. %, or not more than about 11 wt. %, or not more than about 10.5wt. %, or not more than about 10 wt. %, or not more than about 9.5 wt.%, or not more than about 9 wt. %, or in the range of from about 7 toabout 15 wt. %, or about 8 to about 14 wt. %, or about 9 to about 13 wt.%; and the plasticizer content can be less than about 80 phr, or lessthan about 70 phr, or less than about 60 phr, or less than about 50 phrand/or greater than about 10 phr, or greater than about 20 phr, orgreater than about 30 phr. In embodiments, a particularly useful rangefor the residual acetate content from 10 to 18 wt. %, a particularlyuseful range for the residual hydroxyl content is from 9 to 16 wt. %,and a particularly useful range for the plasticizer content ofconventional plasticizer is from 50 to 75 phr. When at least oneplasticizer having at least one aromatic moiety is used, the amount ofplasticizer in the interlayer is higher than the amount of plasticizerin the interlayer not having a plasticizer with at least one aromaticmoiety.

In various embodiments, the polymer interlayer comprises at least afirst poly(vinyl acetal) polymer layer having a first poly(vinyl acetal)resin and a second poly(vinyl acetal) polymer layer having a secondpoly(vinyl acetal) resin wherein at least one of the first and secondpoly(vinyl acetal) layers is the softer layer. The softer layer can havethe residual hydroxyl content, residual acetate content, and plasticizertype and amount within the ranges and limits provided above for thesofter layer and have a glass transition temperature less than 20° C.and a tan delta of greater than 1.33. In other embodiments, one of thefirst and second poly(vinyl butyral) layers is the softer layer and theother layer is the stiffer layer. The first and second poly(vinylacetal) resins in the polymer interlayer can have the same or differentcompositions. For example, in some embodiments, the first poly(vinylacetal) resin can have a residual hydroxyl content and/or residualacetate content that is at least about 0.5, or at least about 1.0, or atleast about 1.5, or at least about 2.0, or at least about 2.5, or atleast about 3.0, at least about 4.0, at least about 5.0, at least about6.0, or at least about 7.0, or at least about 8.0 wt. % higher or lowerthan the residual hydroxyl content and/or residual acetate content ofthe second poly(vinyl acetal) resin. One or more additional poly(vinylacetal) polymer layer(s) may also be present in the interlayer and canhave a residual hydroxyl content and/or a residual acetate contentwithin the ranges provided above. Additionally, the residual hydroxylcontent of the one or more additional poly(vinyl acetal) layer(s) can bethe same as or different from the residual hydroxyl content and/or theresidual acetate content of the first and/or second poly(vinyl acetal)layers.

The difference between the residual hydroxyl content of the first andsecond poly(vinyl acetal) resins could also be at least about 2, atleast about 5, at least about 10, at least about 12, at least about 15,at least about 20, or at least about 30 weight percent (wt. %). As usedherein, the term “weight percent different” or “the difference . . . isat least . . . weight percent” refers to a difference between two givenweight percentages, calculated by subtracting the one number from theother. For example, a poly(vinyl acetal) resin having a residualhydroxyl content of 12 weight percent has a residual hydroxyl contentthat is 2 weight percent lower than a poly(vinyl acetal) resin having aresidual hydroxyl content of 14 weight percent (14 weight percent−12weight percent=2 weight percent). As used herein, the term “different”can refer to a value that is higher than or lower than another value.One or more other poly(vinyl acetal) layers may also be present in theinterlayer and can have a residual hydroxyl within the ranges providedabove. Additionally, the residual hydroxyl content of the one or moreother poly(vinyl acetal) resins can be the same as or different than theresidual hydroxyl content of the first and/or second poly(vinyl acetal)resins.

In some embodiments, the difference between the residual acetate contentof the first and second poly(vinyl acetal) resins can be at least about2, at least about 3, at least about 4, at least about 5, at least about6, at least about 7, at least about 8, at least about 9, or at leastabout 10 weight percent, at least about 12, at least about 14, at leastabout 16, at least about 18, at least about 20, at least about 24, or atleast 29 weight percent. One of the poly(vinyl acetal) resins may have aresidual acetate content of not more than about 4, not more than about3, not more than about 2, or not more than about 1 weight percent,measured as described above. In some embodiments, one of the first andsecond poly(vinyl acetal) resins can have a residual acetate content ofat least about 4, at least about 5, at least about 6, at least about 7,at least about 8, at least about 9, at least about 10, at least about12, at least about 14, at least about 16, at least about 18, at leastabout 20, at least about 25, or at least about 30 weight percent. Inother embodiments, the first and second poly(vinyl acetate) resins bothcan have a residual acetate content of at least 4, at least about 5, atleast about 6, at least about 7, at least about 8, at least about 9, atleast about 10, at least about 12, at least about 14, at least about 16,at least about 18, or at least about 20 wt. %. The difference in theresidual acetate content between the first and second poly(vinyl acetal)resins can be within the ranges provided above, or the difference can beless than about 3, not more than about 2, not more than about 1, or notmore than about 0.5 weight percent. Additional poly(vinyl acetal) layerspresent in the interlayer can have a residual acetate content the sameas or different from the residual acetate content of the first and/orsecond poly(vinyl acetal) resin.

In some embodiments, the difference between the residual hydroxylcontent of the first and second poly(vinyl acetal) resins can be lessthan about 2, not more than about 1, not more than about 0.5 weightpercent and the difference in the residual acetate content between thefirst and second poly(vinyl acetal) resins can be at least about 3, atleast about 4, at least about 5, at least about 6, at least about 7, atleast about 8, at least about 10, at least about 15, at least about 20,or at least about 30 weight percent. In other embodiments, thedifference in the residual acetate content of the first and secondpoly(vinyl acetal) resins can be less than about 3, not more than about2, not more than about 1, or not more than about 0.5 weight percent andthe difference in the residual hydroxyl content of the first and secondpoly(vinyl acetal) resins can be at least about 2, at least about 5, atleast about 10, at least about 12, at least about 15, at least about 20,or at least about 30 weight percent.

In embodiments, at least one of the difference between the firstresidual hydroxyl content and the second residual hydroxyl content andthe difference between the first residual acetate content and the secondresidual acetate content is at least 2.0 weight percent, or thedifference between the first residual hydroxyl content and the secondresidual hydroxyl content and the difference between the first residualacetate content and the second residual acetate content are both atleast 2.0 weight percent, or the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least2.0 weight percent and the difference between the first residual acetatecontent and the second residual acetate content is less than 2.0 weightpercent, or the difference between the first residual hydroxyl contentand the second residual hydroxyl content is less than 2.0 weight percentand the difference between the first residual acetate content and thesecond residual acetate content is at least 2.0 weight percent.

In various embodiments, the differences in residual hydroxyl and/orresidual acetate content of the first and second poly(vinyl acetal)resins can be selected to control or provide certain performanceproperties, such as strength, impact resistance, penetration resistance,processability, or acoustic performance to the final composition, layer,or interlayer. For example, poly(vinyl acetal) resins having a higherresidual hydroxyl content, such as greater than about 16 weight percent,can facilitate high impact resistance, penetration resistance, andstrength to a resin composition or layer, while lower hydroxyl contentresins, such as having a residual hydroxyl content of less than 15weight percent, can improve the acoustic performance of the interlayer.

In various embodiments of the interlayers comprising a softer poly(vinylacetal) layer and a stiffer poly(vinyl acetal) layer, the softer layercan comprise the plasticizer(s) in the ranges and limits provided above,and the stiffer layer can have a plasticizer content of at least 8 phrless than the plasticizer content in the softer layer, or at least 10phr, or at least 12 phr, or at least 14 phr, or at least 16 phr, or atleast 18 phr, or at least 20 phr, or at least 22 phr, or at least 24phr, or at least 26 phr, or at least 28 phr, or at least 30 phr, or atleast 32 phr, or at least 34 phr, or at least 36 phr, or at least 38phr, or at least 40 phr, or at least 45 phr, or at least 50 phr lessthan the plasticizer content in the softer layer. Each respectivelayer's plasticizer content at the equilibrium state is determined bythe layer's respective residual hydroxyl contents and/or residualacetate contents, as disclosed in U.S. Pat. No. 7,510,771 (the entiredisclosure of which is incorporated herein by reference).

The plasticizer content in the stiffer (or skin) layer(s) or softer (orcore) layer(s) can be different from the total plasticizer content. Thetotal plasticizer content can be from 0 to 120 phr, or greater than 0phr, or greater than 5 phr, or greater than 10 phr, or greater than 15phr, or greater than 20 phr, or greater than 25 phr, or greater than 30phr and/or 120 phr or less, or 115 phr or less, or 110 phr or less, or105 phr or less, or 100 phr or less, or 95 phr or less, or 90 phr orless, or 85 phr or less, or 80 phr or less, or 75 phr or less, or 70 phror less, or within the range of 10 to 100 phr, or 20 to 80 phr, or 30 to70 phr. In addition, the stiffer (or skin) layer(s) and softer (or core)layer(s) can have different plasticizer types and plasticizer contents,in the ranges previously discussed. For example, at equilibrium theinterlayer could comprise two stiffer skin layers, each with 38 phrplasticizer, and a softer core layer with 75 phr plasticizer, for atotal plasticizer amount for the interlayer of about 54.3 phr when thecombined skin layer thickness equals that of the core layer.

The interlayers of the present disclosure may have glass transitiontemperatures of about 26° C. or greater, about 30° C. or greater, orabout 35° C. or greater for the stiffer layer(s), and about 10° C. orless, or about 4° C. or less, or about −5° C. or less, or about −10° C.or less for the soft layer(s). In some embodiments, the multilayeredinterlayers of the present disclosure combine these two advantageousproperties (i.e., strength and acoustic) by utilizing harder or stifferskin layers laminated with a softer core layer (e.g.,stiff//soft//stiff) and softer skin layers laminated with a stiffer corelayer (e.g., soft//stiff//soft), while also maintaining other importantperformance properties. In various embodiments, the multilayeredinterlayers generally comprise stiffer layer(s) with a glass transitiontemperature of about 26° C. to about 60° C., 26° C. to about 40° C.,about 26° C. to 35° C., about 26° C. or greater, about 30° C. orgreater, and about 35° C. or greater, and softer layer(s) of about 20°C. or less, about 10° C. or less, or about 4° C. or less, or about −5°C. or less, or about −10° C. or less, or in the range of from −20 to 20°C., or −10 to 20° C., or 0 to 10° C., or 15 to 20° C. In embodimentswhere the interlayer comprises a soft layer and a stiff layer, aparticularly useful range for the glass transition temperature of thesoft layer is from about −9 to 9° C. In embodiments where the interlayeris a monolithic interlayer, a particularly useful range for the glasstransition temperature is from about 10 to 19° C. Although many of theembodiments described above refer to the polymer resin as beingpoly(vinyl acetal) resin, it would be understood by one of ordinaryskill in the art that the polymer may be any polymer suitable for use ina multiple layer panel. Typical polymers include, but are not limitedto, polyvinyl acetals (PVA) (such as poly(vinyl butyral) (PVB) orpoly(vinyl isobutyral), an isomer of poly(vinyl butyral) and alsoreferred as PVB or PVisoB, aliphatic polyurethane (PU),poly(ethylene-co-vinyl acetate) (EVA), polyvinylchloride (PVC),poly(vinylchloride-co-methacrylate), polyethylenes, polyolefins,ethylene acrylate ester copolymers, poly(ethylene-co-butyl acrylate),silicone elastomers, epoxy resins, and acid copolymers such asethylene/carboxylic acid copolymers and its ionomers, derived from anyof the foregoing possible thermoplastic resins, combinations of theforegoing, and the like. PVB and its isomer polyvinyl isobutyral,polyvinyl chloride, ionomers, and polyurethane are suitable polymersgenerally for interlayers; PVB and its isomer (PVisoB) are particularlysuitable.

Polyurethanes can have different hardnesses. An exemplary polyurethanepolymer has a Shore A hardness less than 85 per ASTM D-2240. Examples ofpolyurethane polymers are AG8451 and AG5050, aliphatic isocyanatepolyether based polyurethanes having glass transition temperatures lessthan 20° C. (commercially available from Thermedics Inc. of Woburn,Mass.). EVA polymers (or copolymers) can contain various amounts ofvinyl acetate groups. The desirable vinyl acetate content is generallyfrom about 10 to about 90 mol %. EVA with lower vinyl acetate contentcan be used for sound insulation at low temperatures. Theethylene/carboxylic acid copolymers are generallypoly(ethylene-co-methacrylic acid) and poly(ethylene-co-acrylic acid)with the carboxylic acid content from 1 to 25 mole %. Ionomers ofethylene/carboxylic acid copolymers can be obtained by partially orfully neutralizing the copolymers with a base, such as the hydroxide ofalkali (sodium for example) and alkaline metals (magnesium for example),ammonia, or other hydroxides of transition metals such as zinc. Examplesof ionomers of that are suitable include Surlyn® ionomers resins(commercially available from DuPont of Wilmington, Del.).

Examples of exemplary multilayer interlayer constructs include, but arenot limited to, PVB//PVisoB//PVB, where the PVisoB layer comprises twoor more resins having different residual hydroxyl contents or differentpolymer compositions; PVC//PVB//PVC, PU//PVB//PU, Ionomer//PVB//Ionomer,Ionomer//PU//Ionomer, Ionomer//EVA//Ionomer, where the core layer PVB(including PVisoB), PU or EVA comprises two or more resins havingdifferent glass transitions. Alternatively, all layers may all be PVBusing the same or different starting resins, having the same ordifferent residual hydroxyl and residual acetate contents. Othercombinations of resins and polymers will be apparent to those skilled inthe art.

While generally referred to as poly(vinyl acetal) or poly(vinylbutyral), any of the poly(vinyl acetal) resins can include residues ofany suitable aldehyde, such as isobutyraldehyde, as previouslydiscussed. In some embodiments, one or more poly(vinyl acetal) resin caninclude residues of at least one C₁ to C₁₀ aldehyde, or at least one C₄to C₈ aldehyde. Examples of suitable C₄ to C₈ aldehydes can include, butare not limited to, n-butyraldehyde, isobutyraldehyde,2-methylvaleraldehyde, n-hexyl aldehyde, 2-ethylhexyl aldehyde, n-octylaldehyde, and combinations thereof. At least one of the first and secondpoly(vinyl acetal) resins can include at least about 20, at least about30, at least about 40, at least about 50, at least about 60, or at leastabout 70 weight percent of residues of at least one C₄ to C₈ aldehyde,based on the total weight of aldehyde residues of the resin, and/or caninclude not more than about 90, not more than about 85, not more thanabout 80, not more than about 75, not more than about 70, or not morethan about 65 weight percent of at least one C₄ to C₈ aldehyde, or inthe range of from about 20 to about 90, about 30 to about 80, or about40 to about 70 weight percent of at least one C₄ to C₈ aldehyde. The C₄to C₈ aldehyde may be selected from the group listed above, or it can beselected from the group consisting of n-butyraldehyde, isobutyraldehyde,2-ethylhexyl aldehyde, and combinations thereof.

In various embodiments, one or more poly(vinyl acetal) resin may be apolyvinyl n-butyral (PVB) resin. In other embodiments, one or morepoly(vinyl acetal) resin can be a poly(vinyl n-butyral) resin thatmainly comprises residues of n-butyraldehyde, and may, for example,include not more than about 50, not more than about 40, not more thanabout 30, not more than about 20, not more than about 10, not more thanabout 5, or not more than about 2 weight percent of residues of analdehyde other than n-butyraldehyde, based on the total weight of allaldehyde residues of the resin.

In various embodiments, the monolithic interlayer or at least one of thepolymer layers comprises a poly(vinyl acetal) resin, such as poly(vinylbutyral), and a plasticizer. In other embodiments, all polymer layerscomprise poly(vinyl acetal) resins or poly(vinyl butyral) resins andplasticizers.

The PVB resin is produced by known acetalization processes by reactingpolyvinyl alcohol (“PVOH”) with butyraldehyde in the presence of an acidcatalyst, separation, stabilization, and drying of the resin. Suchacetalization processes are disclosed, for example, in U.S. Pat. Nos.2,282,057 and 2,282,026 and Vinyl Acetal Polymers, in Encyclopedia ofPolymer Science & Technology, 3rd edition, Volume 8, pages 381-399, byB. E. Wade (2003), the entire disclosures of which are incorporatedherein by reference. The resin is commercially available in variousforms, for example, as Butvar® Resin from Solutia Inc., a wholly ownedsubsidiary of Eastman Chemical Company.

The PVB resin (or resins) of the present disclosure typically has amolecular weight of greater than 50,000 Daltons, or less than 500,000Daltons, or about 50,000 to about 500,000 Daltons, or about 70,000 toabout 500,000 Daltons, or about 100,000 to about 425,000 Daltons, asmeasured by size exclusion chromatography using low angle laser lightscattering. As used herein, the term “molecular weight” means the weightaverage molecular weight.

Various adhesion control agents (“ACAs”) can be used in the interlayersof the present disclosure to control the adhesion of the interlayersheet to glass. In various embodiments of interlayers of the presentdisclosure, the interlayer can comprise about 0.003 to about 0.15 partsACAs per 100 parts resin; about 0.01 to about 0.10 parts ACAs per 100parts resin; and about 0.01 to about 0.04 parts ACAs per 100 partsresin. Such ACAs, include, but are not limited to, the ACAs disclosed inU.S. Pat. No. 5,728,472 (the entire disclosure of which is incorporatedherein by reference), sodium acetate, potassium acetate, magnesiumbis(2-ethyl butyrate), and/or magnesium bis(2-ethylhexanoate).

Other additives may be incorporated into the interlayer to enhance itsperformance in a final product and impart certain additional propertiesto the interlayer. Such additives include, but are not limited to, dyes,pigments, stabilizers (e.g., ultraviolet stabilizers), antioxidants,anti-blocking agents, flame retardants, IR absorbers or blockers (e.g.,indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB₆) andcesium tungsten oxide), processing aides, flow enhancing additives,lubricants, impact modifiers, nucleating agents, thermal stabilizers, UVabsorbers, dispersants, surfactants, chelating agents, coupling agents,adhesives, primers, reinforcement additives, and fillers, among otheradditives known to those of ordinary skill in the art.

The final interlayer, whether formed from extrusion or co-extrusion orby lamination of multiple layers, generally has a random rough surfacetopography as it is formed through melt fractures of polymer melt as itexits the extrusion die and may additionally be embossed over the randomrough surface on one or both sides (e.g., the skin layers) by any methodof embossment known to one of ordinary skill in the art.

While all methods for the production of polymer interlayer sheets knownto one of ordinary skill in the art are contemplated as possible methodsfor producing the polymer interlayer sheets described herein, thisapplication will focus on polymer interlayer sheets produced through theextrusion and co-extrusion processes. The final multiple layer glasspanel laminate of the present invention are formed using laminationprocesses known in the art.

Generally, the thickness, or gauge, of the polymer interlayer sheet willbe in a range from about 15 mils to 100 mils (about 0.38 mm to about2.54 mm), about 15 mils to 60 mils (about 0.38 mm to about 1.52 mm),about 20 mils to about 50 mils (about 0.51 to 1.27 mm), and about 15mils to about 35 mils (about 0.38 to about 0.89 mm). In variousembodiments, each of the layers, such as the skin and core layers, ofthe multilayer interlayer may have a thickness of about 1 mil to 99 mils(about 0.025 to 2.51 mm), about 1 mil to 59 mils (about 0.025 to 1.50mm), 1 mil to about 29 mils (about 0.025 to 0.74 mm), or about 2 mils toabout 28 mils (about 0.05 to 0.71 mm).

As noted above, the interlayers of the present disclosure may be used asa single layer (monolithic) sheet or a multilayered sheet. In variousembodiments, the interlayers of the present disclosure (either as asingle layer sheet or as a multilayered sheet) can be incorporated intoa multiple layer panel.

As used herein, a multiple layer panel can comprise a single substrate,such as glass, acrylic, or polycarbonate with a polymer interlayer sheetdisposed thereon, and most commonly, with a polymer film furtherdisposed over the polymer interlayer. The combination of polymerinterlayer sheet and polymer film is commonly referred to in the art asa bilayer. A typical multiple layer panel with a bilayer construct is:(glass) II (polymer interlayer sheet) II (polymer film), where thepolymer interlayer sheet can comprise multiple interlayers, as notedabove. The polymer film supplies a smooth, thin, rigid substrate thataffords better optical character than that usually obtained with apolymer interlayer sheet alone and functions as a performance enhancinglayer. Polymer films differ from polymer interlayer sheets, as usedherein, in that polymer films do not themselves provide the necessarypenetration resistance and glass retention properties, but ratherprovide performance improvements, such as infrared absorptioncharacteristics. Poly(ethylene terephthalate) (“PET”) is the mostcommonly used polymer film. Generally, as used herein, a polymer film isthinner than a polymer sheet, such as from about 0.001 to 0.2 mm thick.

Further, the multiple layer panel can be what is commonly known in theart as a solar panel, with the panel further comprising a photovoltaiccell, as that term is understood by one of ordinary skill in the art,encapsulated by the polymer interlayer(s). In such instances, theinterlayer is often laminated over the photovoltaic cell, with aconstruct such as: (glass)//(polymer interlayer)//(photovoltaiccell)//(polymer interlayer)//(glass or polymer film).

The interlayers of the present disclosure will most commonly be utilizedin multiple layer panels comprising two substrates, preferably a pair ofglass sheets (or other rigid materials, such as polycarbonate oracrylic, known in the art), with the interlayers disposed between thetwo substrates. An example of such a construct would be:(glass)//(polymer interlayer sheet)//(glass), where the polymerinterlayer sheet can comprise multilayered interlayers, as noted above.These examples of multiple layer panels are in no way meant to belimiting, as one of ordinary skill in the art would readily recognizethat numerous constructs other than those described above could be madewith the interlayers of the present disclosure.

The typical glass lamination process comprises the following steps: (1)assembly of the two substrates (e.g., glass) and interlayer; (2) heatingthe assembly via an IR radiant or convective means for a short period;(3) passing the assembly into a pressure nip roll for the firstdeairing; (4) heating the assembly a second time to about 60° C. toabout 120° C. to give the assembly enough temporary adhesion to seal theedge of the interlayer; (5) passing the assembly into a second pressurenip roll to further seal the edge of the interlayer and allow furtherhandling; and (6) autoclaving the assembly at temperatures between 135°C. and 150° C. and pressures between 150 psig and 200 psig for about 30to 90 minutes. The actual steps, as well as the times and temperatures,may vary as necessary, as known by one skilled in the art.

Other means for use in de-airing of the interlayer-glass interfaces(steps 2-5) known in the art and that are commercially practiced includevacuum bag and vacuum ring processes in which a vacuum is utilized toremove the air.

The invention also includes the following Embodiments 1 to 15, set forthbelow.

Embodiment 1 is polymer interlayer comprising: a layer comprising apoly(vinyl acetal) resin having a residual hydroxyl content and aresidual acetate content, and a plasticizer, wherein the residualhydroxyl content, the residual acetate content and the plasticizer areselected such that the polymer interlayer has at least one glasstransition temperature less than about 20° C. and a peak tan delta ofgreater than 1.33, and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

Embodiment 2 is a polymer interlayer including the features ofembodiment 1, wherein the plasticizer comprises an aromatic moiety.

Embodiment 3 is a polymer interlayer including the features of any ofembodiments 1 to 2, further comprising a second poly(vinyl acetal)resin.

Embodiment 4 is a polymer interlayer including the features of any ofembodiments 1 to 3, further comprising a second layer.

Embodiment 5 is a polymer interlayer including the features ofembodiment 4, wherein the second layer comprises a second poly(vinylacetal) resin and a second plasticizer.

Embodiment 6 is a polymer interlayer comprising: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has at least one glasstransition temperature less than about 20° C. and a peak tan delta ofgreater than 1.33, and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

Embodiment 7 is a polymer interlayer including the features ofembodiments 6, wherein at least one of the difference between the firstresidual hydroxyl content and the second residual hydroxyl content andthe difference between the first residual acetate content and the secondresidual acetate content is at least 2.0 weight percent.

Embodiment 8 is a polymer interlayer comprising: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has at least one glasstransition temperature less than about 20° C. and a peak tan delta ofgreater than 1.33; and wherein at least one of the difference betweenthe first residual hydroxyl content and the second residual hydroxylcontent and the difference between the first residual acetate contentand the second residual acetate content is at least 2.0 weight percent,and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.

Embodiment 9 is a polymer interlayer including the features of any ofembodiments 6 to 8, wherein the first plasticizer and the secondplasticizer are the same.

Embodiment 10 is a polymer interlayer including the features of any ofembodiments 6 to 8, wherein the first plasticizer and the secondplasticizer are different.

Embodiment 11 is a polymer interlayer including the features of any ofembodiments 6 to 10, wherein at least one of the first plasticizer andthe second plasticizer comprises an aromatic moiety.

Embodiment 12 is a polymer interlayer including the features of any ofembodiments 6 to 11, wherein the polymer interlayer has at least oneglass transition temperature less than about 19° C. and a peak tan deltaof greater than 1.35.

Embodiment 13 is a polymer interlayer including the features of any ofembodiments 6 to 12, wherein the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least2.0 weight percent and the difference between the first residual acetatecontent and the second residual acetate content is at least 2.0 weightpercent.

Embodiment 14 is a polymer interlayer including the features of any ofembodiments 6 to 13, wherein the difference between the first residualhydroxyl content and the second residual hydroxyl content is at least4.0 weight percent.

Embodiment 15 is a polymer interlayer including the features of any ofembodiments 6 to 14, wherein the difference between the first residualacetate content and the second residual acetate content is at least 4.0weight percent.

EXAMPLES

The improvements in sound transmission loss (STL) in an interlayer whenincreasing the tan delta of the interlayer can be most readilyappreciated by a comparison of multilayer interlayers having stifferskin layers and a soft core layer having a higher tan delta to amultilayer interlayer having a soft core layer having a lower tan delta.These Examples demonstrate that by providing a multilayer interlayerhaving a core layer with a higher tan delta improves the soundtransmission loss of the multilayer interlayer and laminate comprisingthe multilayer interlayer.

The interlayers were produced by mixing and melt-extruding mixtures ofpoly(vinyl butyral) resin and plasticizer, and other common additives.The types of resins and plasticizers are listed below and the amounts ofresins and plasticizers used are shown in the Tables below.

Resins Used:

Resin A: Poly(vinyl butyral) having about 19 wt. % residual hydroxylcontent and about 2% residual vinyl acetate content

Resin B: Polyurethane AG5050 (an aliphatic isocyanate polyether basedpolyurethane film available from Thermedics Inc. of Woburn, Mass. foruse with laminated glass)

Resin C*: Poly(vinyl butyral) having about 11 wt. % residual hydroxylcontent and about 2% residual vinyl acetate content

Resin D*: Poly(vinyl butyral) having about 11 wt. % residual hydroxylcontent and about 2% residual vinyl acetate content

Resin E*: Poly(vinyl butyral) having about 11 wt. % residual hydroxylcontent and about 2% residual vinyl acetate content (*Note that whileResins C, D and E have the same residual hydroxyl and residual acetatecontents, Resin C had a wider molecular weight distribution than ResinD, and Resin E was made via a different acetalization process than ResinC)

Resin F: Polyurethane AG8451 (an aliphatic isocyanate polyether basedpolyurethane film commercially available from Thermedics Inc. of Woburn,Mass. for use with laminated glass)

Resin G: Poly(vinyl butyral) having about 16 wt. % residual hydroxylcontent and about 2% residual vinyl acetate content

Plasticizers Used:

3GEH Plasticizer: Tri-ethylene glycol di-2-ethylhexanoate

3GH Plasticizer: Tri-ethylene glycol di-2-ethylbutyrate

DOA Plasticizer: Dioctyl Adipate

4G7 Plasticizer: Tetraethylene glycol diheptanoate

N-40 Plasticizer: Surfonic™ N-40 (available from Huntsman Corporation,The Wandlands, Tex.)

N-60 Plasticizer: Surfonic™ N-60 (available from Huntsman Corporation,The Wandlands, Tex.)

Benzoflex 2088 Plasticizer: Benzoflex 2088 is a benzoate esterplasticizer (available from Eastman Chemical Company)

Benzoflex 9-88 Plasticizer: Benzoflex 9-88 is a benzoate esterplasticizer (available from Eastman Chemical Company)

Benzoflex 1046 Plasticizer: Benzoflex 1046 is a specialty benzoateplasticizer (available from Eastman Chemical Company)

BETP Plasticizer: Bis(butoxyethyl)terephthalate

Multilayer (trilayer) interlayers 1 to 4 were produced using the resinsand plasticizers above, in the amounts shown in Table 1 to demonstratethe effect of different resins and resins having different residualhydroxyl contents on sound insulation properties. The multilayerinterlayers were then laminated with two sheets of 2.3 mm clear glass toproduce multiple layer glass panels A to D of dimension 50 cm×80 cm. Theinterlayers were then measured for glass transition temperature and theglass panels were measured for sound insulation properties. Table 2below shows the results. The glass panels were also measured for SoundTransmission Loss (STL) at 20° C. in accordance with ASTM E90, and theSTL data obtained at 20° C. for glass panels in Table 1 (A to D) areshown in FIG. 1.

TABLE 1 Skin layer Core layer Skin layer Plasticizer PlasticizerPlasticizer Glass 3GEH 3GEH Core layer 3GEH Interlayer Panel Interlayercontent content thickness content thickness No. No. Resin (phr) Resin(phr) (mil) Resin (phr) (mils) A 1 Resin-A 38 Resin-B 0 5 Resin-A 38 35B 2 Resin-A 38 Resin-C 75 5 Resin-A 38 33 C 3 Resin-A 38 Resin-D 75 5Resin-A 38 33 D 4 Resin-A 36 Resin-E 75 5 Resin-A 36 33

TABLE 2 Interlayer (core Weighted TL at layer) glass Average TL atCoincident Glass Interlayer transition 2000-8000 Hz frequency (TL_(c))Panel No. No. temperature (T_(g)), ° C. Peak Tan δ (TL_(w)) dB dB A 12.9 0.53 38.2 34.3 B 2 2.6 1.11 40.9 37.7 C 3 2.7 1.21 41.4 38.4 D 4 2.51.29 42.3 39.7

As shown in Table 2, Glass Panels A to D show increasing transmissionloss (TL), especially in the frequency region from 2000 to 8000 Hz(e.g., the wind noise region), where Glass Panel A has the lowest TL andGlass Panel D has the highest TL. Additionally, as shown in FIG. 1, thetest panels all exhibit coincident effect and the observed coincidentfrequency is at about 5000 Hz. The coincident effect exhibited by thesepanels is shown to decrease in the order of Glass Panel A to Glass PanelD. A glass panel having a higher sound insulation rating will exhibitminimal coincident effect and have higher sound transition loss in thewind noise region (the frequency region of 2000 to 8000 Hz). Thesepanels were then rated for sound insulation performance in wind noisefrequency region in the order of: Panel A <Panel B<Panel C<Panel D.Among these four panels, Panel D has the best (or highest) soundinsulation performance and Panel A the worst (or lowest) performance.

The weighted average TL (TL_(w)) of the panels in wind noise frequencyregion for the Glass Panels A to D is shown in Table 2 above and wascalculated using equation (2), previously described:

TL _(w)=10×log((Σ(10^(TL) i ¹⁰))/k) where i=1 to k, and k=7  (2)

Table 2 shows the glass transition temperature (T_(g)) and peak tandelta (tan δ) of the core layers in Interlayers 1 to 4, as well asTL_(w) and TL_(c) of Glass Panels A to D, which contain Interlayers 1 to4. The interlayers all have similar glass transition temperatures (ofabout 2.5 to 2.9° C., corresponding to the core layers), and as shown inTable 2, as the tan delta increases, the TL_(w) and TL_(c) alsoincreases. Surprisingly, the panels having higher TL_(w) and TL_(c)values (which indicates better sound insulation) contain the interlayershaving the higher peak tan delta values in the core layer. Compare, forexample, Glass Panel A and Glass Panel D, where Glass Panel A containsInterlayer 1 (having a peak tan δ value of 0.53, which is the lowest tanδ of Interlayers 1 to 4) and has the lowest TL_(w) and TL_(c) andtherefore poorer insulation to sound transmission, while Glass Panel Dcontains Interlayer 4 (having peak tan δ value of 1.29, the highest tanδ of interlayers 1 to 4) and has the highest TL_(w) and TL_(c) andbetter insulation to sound transmission. Glass panels containinginterlayers having higher peak tan delta (tan δ) values (in the corelayer) provide better sound insulation.

Monolithic interlayers and glass panels containing the monolithicinterlayers were produced using the resins and plasticizers (and commonadditives) listed above. Table 3 shows the monolithic interlayercompositions and multiple layer glass panels containing the interlayers.Interlayers 5 to 7 were laminated with two sheets of 2.3 mm clear glassto produce multiple layer Glass Panels E to G (having overall dimensionsof 50 cm×80 cm).

TABLE 3 Plasticizer Plasticizer 3GEH 3GH Interlayer Glass Interlayercontent content thickness Panel No. No. Resin (phr) (phr) (mils) E 5Resin-F 0 0 30 F 6 Resin-A 0 50 30 G 7 Resin-G 51 0 30

The glass panels were measured for Sound Transmission Loss (STL) inaccordance with ASTM E90 at 20° C., and the STL data of Glass Panels Eto G are shown in FIG. 2. Glass transition temperature (T_(g)) and peaktan delta (tan δ) of Interlayers 5 to 7 and TL_(w) and TL_(c) of GlassPanels E to G were measured and are summarized in Table 4 below.

TABLE 4 Interlayer (core layer) glass weighted TL at transition averageTL at Coincident Interlayer temperature 2000-8000 Hz frequency (TL_(c))No. (T_(g)), ° C. Tan δ (TL_(w)) dB dB E 18.9 0.67 37.2 35.7 F 19.0 0.9539.3 37.4 G 19.0 1.27 40.0 38.0

As shown in Table 4, Glass panels E to G show increasing transmissionloss (TL), especially in the wind noise region, in the order of GlassPanel E to Glass Panel G. As shown by FIG. 2, the glass panels testeddid not exhibit distinct coincident effect for some of the panels. Thecalculated coincident frequency is at about 4000 Hz. The TL at thecalculated coincident frequency is shown to also increase in the orderof Glass Panel E to Glass Panel G.

The glass panels in Table 4 were rated for sound insulation performancein the wind noise frequency region in the order of: Panel E<PanelF<Panel G. Among these panels, Glass Panel G has the highest or bestsound insulation performance and Glass Panel E has the lowest or worstperformance. The interlayers all have glass transition temperatures ofabout 19° C., and varying tan delta values at the peak of the glasstransitions.

Similar to the glass panels containing multilayer interlayers shownabove in Table 2, glass panels containing monolithic interlayers showthe dependence of sound insulation properties (TL_(w) and TL_(c)) on theinterlayer's tan delta (tan δ). As shown by the data in Table 4, theTL_(w) and TL_(c) both increase with increasing peak tan delta (tan δ)values of the interlayer. Glass Panel E contains Interlayer 5 (havingpeak tan δ of 0.67, which is the lowest among the three Interlayers 5, 6and 7), and it also has the lowest TL_(w) and TL_(c), and thereforepoorer sound insulation. Glass Panel G contains Interlayer 7 (having tanδ of 1.27, which is almost double that of Interlayer 5), the highestamong these Interlayers, and has the highest TL_(w) and TL_(c) andtherefore better sound insulation. Based on the results in Table 4, itis clear that glass panels containing monolithic interlayers exhibitinghigher peak tan delta (tan δ) values provide improved or better (higher)sound insulation.

The previous examples of glass panels comprising multilayer interlayershaving a glass transition temperature of about 3° C. in the core layer,and monolithic interlayers having a glass transition temperature ofabout 19° C., clearly demonstrate that improved and superior soundinsulation of a glass panel can be achieved when the interlayer has aspecific peak tan delta (tan δ) value of greater than about 1.30, orgreater than about 1.33, or even great than about 1.35. Superior soundinsulation performance can be achieved regardless of the interlayer'sstructure and number of layers, as long as the interlayer's peak tan δis greater than about 1.30, or greater than about 1.33, or greater thanabout 1.35, and where the interlayer has a glass transition temperatureless than about 20° C.

Table 5 demonstrates that interlayer sheets can be formulated withvarious resins having different residual hydroxyl and/or residualacetate contents and different plasticizers so that the interlayer has apeak tan delta (tan δ) of greater than 1.30, or greater than 1.33, orgreater than 1.35. The interlayers were produced as described aboveusing the plasticizers listed above. The resins have residual hydroxylcontent and residual acetate content as shown in Table 5. Glasstransition temperature and peak tan delta (tan δ) were measured aspreviously described and are shown below.

TABLE 5 Glass Transition Sheet PVOH PVAc Benzoflex Benzoflex BenzoflexTemperature No. (wt. %) (wt. %) 3GEH DOA 4G7 N-40 N-60 2088 9-88 1046BETP (Tg/° C.) Tan δ 1 10.7 2 60 4.6 1.41 2 11.0 12.0 75 −2 1.37 3 8.522.8 60 1.1 1.80 4 8.5 22.8 75 −7.0 1.50 5 10.7 25.8 60 1.1 1.60 6 10.725.8 75 −7.1 1.40 7 10.0 2 60 3.4 1.35 8 9.5 2 50 8.7 1.47 9 10.0 2 5010.3 1.50 10 10.5 2 50 12.3 1.40 11 10.7 2 50 12.4 1.48 12 10.7 2 50 9.01.35 13 10.7 2 50 3.5 1.45 14 10.7 2 60 −2.8 1.38 15 10.7 2 60 13.7 1.6216 10.7 2 70 7.4 1.52 17 10.7 2 60 11.3 1.49 18 10.7 2 70 6.8 1.43 1910.7 2 60 10.5 1.65 20 10.7 2 70 6.4 1.60 21 10.7 2 80 2.5 1.57 22 10.72 40 40 −3.8 1.35 23 9.5 2 60 8.6 1.60 24 9.5 2 70 4.9 1.54 25 9.5 2 801.5 1.46 26 9.5 2 90 −1.4 1.47 27 10.7 2 70 11.4 1.54 28 10.7 2 80 8.51.51 29 10.7 2 90 4.6 1.49 30 10.7 2 100 2.3 1.46 31 10.5 2 70 14.3 1.4032 10.5 2 76 3 1.34 33 10.7 2 50 15.9 1.66 34 10.7 2 50 15.9 1.55 3510.7 2 50 16.4 1.70 36 10.7 2 60 16.1 1.59 37 10.5 2 60 18.5 1.50 3810.7 2 40 18.5 1.56

Table 5 shows that interlayers can be produced using different resinshaving different residual hydroxyl and/or residual acetate contents, andwith different plasticizers, to obtain interlayers having a combinationof a glass transition temperature less than 20° C. and a peak tan delta(tan δ) of at least 1.30, or greater than 1.33, or greater than 1.35.These interlayers can then be used either alone or in combination withother interlayers to produce glass panels having improved soundinsulation.

Interlayer sheets 1 to 6 contain resins having residual hydroxyl levelsof about 8 to about 11 wt. % and residual vinyl acetate levels of about2 to 26 wt. %, and 3GEH plasticizer in amounts of from 60 to 75 phr.Interlayer sheets 1 to 6 exhibit glass transition temperatures of from−7.1 to 4.6° C. and have peak tan delta (tan δ) values of 1.37 to 1.80at the glass transition. Multilayer interlayers comprising interlayersheets 1 to 6 as the core layers can be stably formulated with minimumplasticizer migration between adjacent skin and core layers by choosingskin layer resins to have residual hydroxyl content about 19 to 21 wt. %and plasticizer content about 30 to 36 phr, thus producing multilayerinterlayers that have glass transition temperatures between −7.1 to 4.6°C. and peak tan delta (tan δ) values between 1.37 and 1.80.

Interlayer sheets 7 to 14 contain resins having residual hydroxyl levelsof about 9.5 to about 11 wt. %, residual vinyl acetate levels of about 2wt. %, and different conventional plasticizers at levels of from 50 to60 phr. Interlayer sheets 7 to 14 exhibit glass transition temperaturesof from −2.8 to 12.4° C. and have peak tan delta (tan δ) values of 1.35to 1.50 at the glass transition. Multilayer interlayers comprisinginterlayer sheets 7 to 14 as core layers can be stably formulated withminimum plasticizer migration between adjacent skin and core layers bychoosing skin layer resins to have residual hydroxyl contents of about19 to 20 wt. % and a plasticizer that is the same plasticizer as in thecore layer in amounts of about 25 to 30 phr, thus maintaininginterlayers having glass transition temperatures between −2.8 and 12.4°C. and peak tan delta (tan δ) values between 1.35 and 1.50.

Interlayer sheets 15 to 32 contain resins having residual hydroxyllevels of about 9.5 to about 11 wt. %, residual vinyl acetate levels ofabout 2 wt. %, and comprise plasticizers containing at least onearomatic moiety, or in the case of interlayer sheet 22, a blend of aconventional plasticizer and a plasticizer containing at least onearomatic moiety, at levels of from 60 to 100 phr. Sheets 15 to 32exhibit glass transition temperatures of from −3.8 to 14.3° C. and havepeak tan delta (tan δ) values of 1.34 to 1.62 at the glass transition.Comparing to the interlayer sheets containing conventional plasticizers(Interlayer sheets 7 to 14), sheets containing plasticizers having atleast one aromatic moiety exhibit higher peak tan delta (tan δ) values.Multilayer interlayers comprising interlayer sheets 15 to 32 as corelayers can be stably formulated with minimum plasticizer migrationbetween adjacent skin and core layers by choosing skin layer resins tohave residual hydroxyl contents of about 19 to 23 wt. % and aplasticizer that is the same plasticizer as in the core layer in amountsof about 30 to 50 phr, thus maintaining interlayers having glasstransition temperatures between −3.8 and 14.3° C. and peak tan delta(tan δ) values between 1.34 and 1.62. All of interlayer sheets 7 to 32have glass transition temperatures of less than 20° C. and peak tandelta values of at least 1.33.

Interlayer sheets 33 to 38 contain resins having residual hydroxylcontents of about 11 wt. % (10.5 to 10.7 wt. %), residual vinyl acetatecontents of about 2 wt. %, and various conventional plasticizers andplasticizers having at least one aromatic moiety in amounts of from 40to 60 phr. Interlayer sheets 33 to 38 have glass transition temperaturesfrom about 16 to 19° C. and peak tan delta (tan δ) values of 1.50 to1.70 and can be used as monolithic interlayer, or as the core layer inmultilayer interlayer compositions. Again, all of the interlayer sheets33 to 38 have glass transition temperatures of less than 20° C. and peaktan delta values of at least 1.33, or in this case, at least 1.50.

One example of an exemplary multilayer interlayer containing a corelayer from Table 5 (Interlayer Sheet 32) is compared to a multilayerinterlayer containing a core layer in Interlayer 2 from Table 1, isshown in Table 6. Glass Panel B is described in Table 2. Glass Panel Hcomprises Interlayer 8 comprising Interlayer Sheet 32 (Table 5) as acore layer, and skin layers comprising the same resin as the skin layersof Interlayer 2. The interlayer 2 in Glass Panel B comprises aconventional plasticizer (3GEH), while the interlayer 8 in Glass Panel Hcomprises BETP, a plasticizer having at least one aromatic moiety.

Table 7 summarizes the glass transition temperature (T_(g)) and peak tandelta (tan δ) of the core layers in Interlayers 2 and 8, as well asTL_(w) and TL_(c) of the glass panels B and H containing Interlayers 2and 8.

TABLE 6 Skin layer Core layer Skin layer Plasticizer PlasticizerPlasticizer Plasticizer Plasticizer Plasticizer Glass 3GEH BETP 3GEHBETP Core layer 3GEH BETP Interlayer panel Interlayer content contentcontent content thickness content content thickness No. No. Resin (phr)(phr) Resin (phr) (phr) (mil) Resin (phr) (phr) (mils) B 2 Resin-A 38Resin-C 75 5 Resin-A 38 33 H 8 Resin-A 41 Resin-C 76 5 Resin-A 41 33

TABLE 7 Interlayer (core weighted TL at layer) glass average TL atCoincident Glass Interlayer transition 2000-8000 Hz frequency (TL_(c))panel No. No. temperature (T_(g)), ° C. Peak Tan δ (TL_(w)) dB dB B 22.6 1.11 40.9 37.7 H 8 3 1.34 42.6 38.5

The comparative interlayer (Interlayer 2) and disclosed interlayer(Interlayer 8) contain the same resins for skin and core but differentplasticizers. The plasticizer does not migrate between the skin and corelayers, but instead the multilayer interlayer is stably formulated tomaintain the plasticizer differences between skin and core layers.

Table 7 shows that Glass Panel H, which contains Interlayer 8 (having aglass transition temperature of about 3° C. and a peak tan delta (tan δ)of 1.34), has better sound insulation than Glass Panel B.

Selecting the resin properties, and more specifically, the residualhydroxyl and/or residual acetate contents, as well as the plasticizer,provides the ability to produce an interlayer having a higher peak tandelta (tan δ) as well as a glass transition temperature below a certainlevel (such as below 20° C.). By selecting the resin and plasticizer toincrease the peak tan delta of an interlayer, it is possible to increasethe transmission loss of a glass panel that includes the interlayer, andthe interlayer produced has better sound insulating properties whenincluded in a glass panel.

While the invention has been disclosed in conjunction with a descriptionof certain embodiments, including those that are currently believed tobe the preferred embodiments, the detailed description is intended to beillustrative and should not be understood to limit the scope of thepresent disclosure. As would be understood by one of ordinary skill inthe art, embodiments other than those described in detail herein areencompassed by the present invention. Modifications and variations ofthe described embodiments may be made without departing from the spiritand scope of the invention.

It will further be understood that any of the ranges, values, orcharacteristics given for any single component of the present disclosurecan be used interchangeably with any ranges, values or characteristicsgiven for any of the other components of the disclosure, wherecompatible, to form an embodiment having defined values for each of thecomponents, as given herein throughout. For example, an interlayer canbe formed comprising poly(vinyl butyral) having a residual hydroxylcontent in any of the ranges given in addition to comprising aplasticizers in any of the ranges given to form many permutations thatare within the scope of the present disclosure, but that would becumbersome to list. Further, ranges provided for a genus or a category,such as phthalates or benzoates, can also be applied to species withinthe genus or members of the category, such as dioctyl terephthalate,unless otherwise noted.

What is claimed is:
 1. A polymer interlayer comprising: a layercomprising a poly(vinyl acetal) resin having a residual hydroxyl contentand a residual acetate content, and a plasticizer, wherein the residualhydroxyl content, the residual acetate content and the plasticizer areselected such that the polymer interlayer has at least one glasstransition temperature less than about 20° C. and a peak tan delta ofgreater than 1.33, and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.
 2. Thepolymer interlayer of claim 1, wherein the plasticizer comprises anaromatic moiety.
 3. The polymer interlayer of claim 1, furthercomprising a second plasticizer.
 4. The polymer interlayer of claim 1,further comprising a second poly(vinyl acetal) resin.
 5. The polymerinterlayer of claim 1, further comprising a second layer.
 6. The polymerinterlayer of claim 5, wherein the second layer comprises a secondpoly(vinyl acetal) resin and a second plasticizer.
 7. A polymerinterlayer comprising: a first layer comprising a first poly(vinylacetal) resin having a first residual hydroxyl content and a firstresidual acetate content, and a first plasticizer; and a second layercomprising a second poly(vinyl acetal) resin having a second residualhydroxyl content and a second residual acetate content, and a secondplasticizer; wherein the residual hydroxyl contents, the residualacetate contents and the plasticizers are selected such that the polymerinterlayer has at least one glass transition temperature less than about20° C. and a peak tan delta of greater than 1.33, and a glass panelhaving a configuration of 2.3-mm glass//interlayer//2.3-mm glass and at20° C. has a transmission loss, TL_(w), of greater than 42 decibels asmeasured by weighted average sound transmission loss at 2000 to 8000 Hz,and a transmission loss, TL_(c), of greater than 38 decibels at thecoincident frequency.
 8. The polymer interlayer of claim 7, wherein thefirst plasticizer and the second plasticizer are the same.
 9. Thepolymer interlayer of claim 7, wherein the first plasticizer and thesecond plasticizer are different.
 10. The polymer interlayer of claim 7,wherein at least one of the first plasticizer and the second plasticizercomprises an aromatic moiety.
 11. The polymer interlayer of claim 7,wherein at least one of the difference between the first residualhydroxyl content and the second residual hydroxyl content and thedifference between the first residual acetate content and the secondresidual acetate content is at least 2.0 weight percent.
 12. The polymerinterlayer of claim 7, wherein the polymer interlayer has at least oneglass transition temperature less than about 19° C. and a peak tan deltaof greater than 1.35.
 13. A polymer interlayer comprising: a first layercomprising a first poly(vinyl acetal) resin having a first residualhydroxyl content and a first residual acetate content, and a firstplasticizer; and a second layer comprising a second poly(vinyl acetal)resin having a second residual hydroxyl content and a second residualacetate content, and a second plasticizer; wherein the residual hydroxylcontents, the residual acetate contents and the plasticizers areselected such that the polymer interlayer has at least one glasstransition temperature less than about 20° C. and a peak tan delta ofgreater than 1.33; and wherein at least one of the difference betweenthe first residual hydroxyl content and the second residual hydroxylcontent and the difference between the first residual acetate contentand the second residual acetate content is at least 2.0 weight percent,and a glass panel having a configuration of 2.3-mmglass//interlayer//2.3-mm glass and at 20° C. has a transmission loss,TL_(w), of greater than 42 decibels as measured by weighted averagesound transmission loss at 2000 to 8000 Hz, and a transmission loss,TL_(c), of greater than 38 decibels at the coincident frequency.
 14. Thepolymer interlayer of claim 13, wherein the difference between the firstresidual hydroxyl content and the second residual hydroxyl content is atleast 2.0 weight percent and the difference between the first residualacetate content and the second residual acetate content is at least 2.0weight percent.
 15. The polymer interlayer of claim 13, wherein thedifference between the first residual hydroxyl content and the secondresidual hydroxyl content is at least 4.0 weight percent.
 16. Thepolymer interlayer of claim 13, wherein the difference between the firstresidual acetate content and the second residual acetate content is atleast 4.0 weight percent.
 17. The polymer interlayer of claim 13,wherein the polymer interlayer has at least one glass transitiontemperature less than about 19° C. and a peak tan delta of greater than1.35.
 18. The polymer interlayer of claim 13, wherein the firstplasticizer and the second plasticizer are the same.
 19. The polymerinterlayer of claim 13, wherein the first plasticizer and the secondplasticizer are different.
 20. The polymer interlayer of claim 13,wherein at least one of the first plasticizer and the second plasticizercomprises an aromatic moiety.